Regenerator burners generally are industrial burners which operate with regenerative air preheating. Further, regenerative burners, as a rule, operate with two integrated regenerators which are alternately acted upon by hot combustion waste gases and by cold combustion air in counterflow operation. Such regenerator burners make it possible to achieve a higher air preheating than so-called recuperator burners, i.e. industrial burners that have a built-in recuperator. The relative air preheating achievable in regenerator burners amounts to up to 90%, i.e. with an exhaust gas entry temperature of, for example, 1000.degree. C. the combustion air can be preheated to approximately 900.degree. C.
Because of the high air preheating, industrial burners with integrated regenerators operate with a very good efficiency, however, as a rule, they require measures for the reduction of NO.sub.X.
An example of such a regenerator burner is described in applicant's EP 0 685 683 A3. With this regenerator burner, a single coaxially traversed regenerator is provided in an annular space coaxially surrounding the fuel lance, the heat storage elements of the regenerator consist of individual ceramic regenerator disks which are stacked on one another. A ceramic combustion chamber is engaged on the outlet side of the regenerator which issues--over a nozzle the cross section of which is approximately cloverleaf--into the furnace chamber and in which gas and air are burned until the ignition temperature in the furnace space (approximately 800.degree. C.) is achieved. Once the ignition temperature is achieved, the gas feed for the combustion in the furnace space is switched over. Since the regenerator burner is equipped only with one regenerator, it is thereupon operated step-wise in two operating cycles. During a first operating cycle, the burner's regenerator is traversed by hot exhaust gases from the furnace with shut-off fuel and combustion air feed, these exhaust gases heating up the heat storage elements of the regenerator. As soon as the regenerator is heated up, the second operating cycle is initiated by a corresponding switch-over of an exhaust-gas and combustion air valve. In the second operating cycle, the heat storage disks of the regenerator are traversed in a reversed direction by the combustion air and thereupon the combustion air is preheated before its entry into the combustion chamber and from there into the furnace space. Because of this cyclic operation, in practice, at least two regenerator burners of this type which are driven in pairs so as to be acted upon alternately with combustion and furnace exhaust gas are required. In many cases, the arrangement of the two burners does not cause any trouble--for example with direct heating or with jet tubes having two shanks as is also explained in this reference. A similar arrangement having two generator burners, the regenerators of which clearly lie outside of the furnace wall, is described in EP 0 293 168 A2.
With another regenerator burner disclosed in applicant's EP 0 463 218 A3, the arrangement is constructed in such a way that 6 regenerator cartridges that lie in the opening of the furnace wall receiving the burner are arranged radially spaced about a coaxial air conducting cylinder enclosing the fuel lance. Each of the regenerator cartridges comprises a number of ceramic storage stones containing continuous flow channels are stacked one over another and arranged one after another for the flow. The regenerator cartridges are provided in each case with a tubular outer mantel of sheet steel which receives the storage stones and on which there is connected, on the side facing the furnace space, a nozzle chamber in the bottom wall of which, in each case, two nozzles are arranged. All the nozzles of the regenerator cartridges lie on an imaginary circle, coaxial to the fuel lance, in which adjacent nozzles have an equal axial spacing. The nozzle chambers of the regenerator cartridges enclose a ceramic combustion chamber which is connected to the air-conducting cylinder and into which the fuel lance discharges. The combustion chamber makes it possible to achieve the necessary ignition temperature of approximately 800.degree. C. in the furnace space. The regenerator cartridges are operated group-wise in one of two operating cycles. In one operating cycle, the regenerator cartridges are traversed and heated up by the hot combustion exhaust gases, while in the other operating cycle regenerator cartridges give off the stored heat to the cold combustion air traversing them. Between the cylindrical regenerator cartridges a considerable unused gusset volume remains, so that the heat storage capacity of the regenerators is limited.
A fundamentally similar problem also applies, finally, for a regenerator burner described in EP 0 715 123 A2. With this regenerator burner, the two regenerators are arranged within a tube coaxial to the central fuel lance and are formed in one embodiment by a number of regenerator cartridges lying on a common imaginary circle, and in another embodiment the regenerator cartridges are arranged in an annular space which is coaxial to the fuel lance and is subdivided by the radial partition walls. The sector-form subdivisions contain the heat storage elements stacked one upon another and which in one example comprise ceramic honeycomb stones. The alternating action of hot combustion gases or cold combustion air on the two regenerators occurs through a valve arrangement which has two perforated disks which are turnable against one another. While with the embodiment with the regenerator cartridges arranged in wreath form there is significant unused gusset volume, production of the second embodiment is complicated if the cylindrical tube receiving the heat storage elements and the radial partition walls installed in this tube are made of a ceramic material. In particular, sealing problems arise along with other problems.